The present invention relates to an arrangement for aerating of liquids, which is particularly although not exclusively suitable for use in aerobic microbiological processes, such as for instance the case in the production of antibiotics, the growing of microorganisms and in chemical gas reactions.
I wish it to be understood that the term "aerating" as used in the following description and in the appended claims is intended not merely to refer to the mixing of liquid with air, but in fact to the mixing of liquid with any type of gas.
It is well known that the more intensive the aeration of liquid in the case of an aerobic fermentation process, the better the growth of the microorganisms which can be obtained. It is also known that the smaller the gas bubbles which are added into the liquid, the better will be the gas-liquid exchange that can take place. Heretofore, however, the prior art in its proposals for the aerating of liquids has always assumed that a relatively uniform liquid medium is to be subjected to aeration. However, this is by no means always the case.
Thus, the aerating of a medium which, for instance, may contain yeast poses requirements which are entirely different from those of other media, for instance a liquid medium containing penicillin (Mycel). Moreover, neither of these exemplary circumstances involves a Newtonian liquid.
One type of aerating apparatus that has been proposed in the prior art uses rotors which are provided at their periphery with gas outlet openings which communicate with an inlet opening and wherein a flow of the gas is established and maintained due to suction resulting from the centrifugal ejection of the gas through the outlet openings. This type of equipment is for instance described in H. G. Rehm, Industrial Microbiology, page 66, Berlin, Heidelberg, New York, 1967. The difficulty encountered with this type of equipment has been that in order to obtain the necessary suction effect, the rotors must turn at rather high speed, which means that if the liquid in which they turn and which is to be aerated is relatively viscous, the equipment will work either very poorly or not at all. The pressure head of the gas is small and not controllable.